In long term evolution (LTE) that is a cellular communication scheme standardized in the third generation partnership project (3GPP), as a bandwidth used for radio communication, 6 alternatives of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz are defined (see, for example, Non-Patent Literature 1). In LTE-advanced (LTE-A) obtained by developing the LTE, technology called carrier aggregation is further introduced, which allows a plurality of component carriers each having any bandwidth described above to be integrally used. For example, when the two component carriers each having a bandwidth of 20 MHz are simultaneously used, it is possible to form a radio channel of 40 MHz in total.
However, frequency bands assigned to communication providers in each country are not always adapted to the bandwidths defined in the LTE (hereinafter, a term of the LTE also includes the LTE-A). Therefore, when the communication providers operate an LTE system, an excess frequency band may remain as it is without being used. Then, a concept called band-filling has been proposed, in which an extension band is set to the excess frequency band adjacent to the component carrier, and the extension band is also used for radio communication, in order to improve utilization efficiency of frequency resources (see, for example, Non-Patent Literature 2).